Effect of Active Layer Thickness on Open Circuit Voltage in Organic Photovoltaic Devices

The effect of active layer thickness has been investigated on open circuit voltage ( V oc ) in bilayer organic photovoltaic (OPV) devices. V oc has been found to vary nonlinearly with the active layer thickness even with the same donor/acceptor materials. We present a model which gives a nonlinear variation of built-in voltage ( V bi ) with the active layer thickness. The nonlinear variation of V oc with active layer thickness has been attributed to the variation of V bi in the samples. The investigations reported here suggest that V bi controls the V oc in OPV devices.